Unable to add custom properties in UI Configuration mode on Linux

[F3ynix]

Hello,

When I enter in configuration mode (both for models where I look for setting up UI and models which already have UI added), if I try to add anything as custom property using right-click with "Add to MustardUI (Unsorted)" or any other option to add a custom property, it always fails with the following output in terminal/console:

Traceback (most recent call last):
File "/home/f3ynix/.config/blender/5.0/extensions/blender_org/MustardUI/custom_properties/ops_props.py", line 63, in execute
rna, path = clipboard.rsplit('.', 1)
^^^^^^^^^
ValueError: not enough values to unpack (expected 2, got 1)
03:09.645  bpy.rna          | ERROR Python script error in MUSTARDUI_OT_property_menuadd.execute
03:09.645  operator         | ERROR Python: Traceback (most recent call last):
|   File "/home/f3ynix/.config/blender/5.0/extensions/blender_org/MustardUI/custom_properties/ops_props.py", line 63, in execute
|     rna, path = clipboard.rsplit('.', 1)
|     ^^^^^^^^^
| ValueError: not enough values to unpack (expected 2, got 1)

I'll finally give some informations about my setup and the UI version used:

Distro: Garuda Linux (based on Arch Linux); also tested with CachyOS and Fedora with same results
Blender version: 5.0.1
MustardUI: 2026.2.1 (same result on previous versions)

[Mustard2]

Thanks for the report! What kind of custom property are you trying to add?

[F3ynix]

Shape keys, color from color node, value from a math node, modifier value, modifier visibility, particles viewport/render amount, etc.

Everything I tested gives the same python error in terminal.

[Mustard2]

Ok this might be more complex than I thought. :(

The issue might be solved by

def mustardui_get_prop_path(ptr, prop):
    # Get full data path including the owning ID
    id_data = ptr.id_data  # The root ID (Object, Mesh, etc.)
    rna_path = ptr.path_from_id()  # Relative path from that ID
    prop_name = prop.identifier

    # Combine with id_data
    if isinstance(id_data, bpy.types.ID):
        full_path = f"bpy.data.{id_data.bl_rna.name.lower()}['{id_data.name}']"
        if rna_path:
            full_path += f".{rna_path}"
    else:
        full_path = rna_path

    return full_path, prop_name

Called in

ptr = context.button_pointer
prop = context.button_prop

if not ptr or not prop:
    self.report({'ERROR'}, "No property selected.")
    return {'CANCELLED'}

rna, path = mustardui_get_prop_path(ptr, prop)

But it doesn't seem to work in general. I'll have to find another solution.

[Mustard2]

Hi @F3ynix, it might be a problem of Wayland.

Can you try to run Blender with

GDK_BACKEND=x11 blender

This should force the use of X11 instead.

[F3ynix]

Hello!

I followed what you said by copy-pasting your command in terminal, but it doesn't work neither. I'm still getting this when trying to add anything as custom property, unfortunately 😢

Traceback (most recent call last):
File "/home/r4ynix/.config/blender/5.0/extensions/blender_org/MustardUI/custom_properties/ops_props.py", line 63, in execute
rna, path = clipboard.rsplit('.', 1)
^^^^^^^^^
ValueError: not enough values to unpack (expected 2, got 1)
00:47.039  bpy.rna          | ERROR Python script error in MUSTARDUI_OT_property_menuadd.execute
00:47.039  operator         | ERROR Python: Traceback (most recent call last):
|   File "/home/f3ynix/.config/blender/5.0/extensions/blender_org/MustardUI/custom_properties/ops_props.py", line 63, in execute
|     rna, path = clipboard.rsplit('.', 1)
|     ^^^^^^^^^
| ValueError: not enough values to unpack (expected 2, got 1)

[Mustard2]

I'll have to find a way to reproduce it, because I don't have Linux installed. I will try to setup a VM on Mac.

[Mustard2]

Hi @F3ynix ! In Blender 5.1 some improvements has been made with Wayland. Can you check if the same issue is still there in Blender 5.1 when you have time?

[F3ynix]

Hi @Mustard2 ! 5.1 just arrived in Arch repo and... welp... no change at all 😔

[Mustard2]

Then I'll try on a VM I guess, I'm really puzzled here. :(

[F3ynix]

Very sorry for this, I hoped you could solve this with less trouble :'(

[Mustard2]

No worries, it's definitely not your fault. It's Blender being Blender :D

[Mustard2]

Update: tried on Ubuntu, no problem there.

[F3ynix]

Hum that's interesting. It means that the problem doesn't appear for all distros 🤔