pyside6-designer does not set environment for editable Python packages correctly

While using pyenv + pyside, the pyside-designer starts, finds plugins correctly but fails to import third-party libraries that are installed in the pyenv environment. I was able to reproduce the issue also with venvs (virtual environments). However, when started using conda, the environment seems to be resolved correctly and the plugin works as expected. 

Example pyenv:

"DYLD_INSERT_LIBRARIES": "/Users/user_name/.pyenv/versions/3.12.2/lib/libpython3.12.dylib",
"PYSIDE_DESIGNER_PLUGINS": "/Users/user_name/examples/plugin_example_pyside",

cmd:
/Users/user_name/.pyenv/versions/3.12.2/envs/pyside_debug/lib/python3.12/site-packages/PySide6/Designer.app/Contents/MacOS/Designer

 
Example conda:

"DYLD_INSERT_LIBRARIES": "/Users/user_name/anaconda3/envs/pyside_debug/lib/libpython3.11.dylib",
"PYSIDE_DESIGNER_PLUGINS": "/Users/user_name/examples/plugin_example_pyside",

cmd: 
/Users/user_name/anaconda3/envs/pyside_debug/lib/python3.11/site-packages/PySide6/Designer.app/Contents/MacOS/Designer

 
When launched with pyenv or venv, the designer reports that the third-party dependency (bec_widgets) cannot be imported:

qt.pysideplugin: Error running /Users/user_name/examples/plugin_example_pyside/registertictactoe.py: No module named 'bec_widgets' 

(registertictactoe imports "bec_widgets")
 
Same plugin code with conda works. 
 
Both scenarios were tested on 
PySide6             6.7.2
PySide6_Addons      6.7.2
PySide6_Essentials  6.7.2
 
Is there anything that must be set up differently for pyenv and venvs from conda environments?
 
Thanks in advance for any guidance you can provide!