The feature constructor widget deletes all the new variable definitions when you change variables in upstream widgets, it deletes even new variables that do not use the changed variables.

For example, I use an Integrate spectra widget to create variables that I then ratio against each other in the Feature constructor. If I modify or delete one of the integrated variables in teh upstream widget, all variables creatd in the Feature constructor disappear, even those that do not use the modified variable.

I uploaded a worflow that can be used to reproduce the bug. It uses data from the repository accessed with the Dataset widget.

I use Orange '3.29.3' in Quasar 1.2 on Windows X
Quasar was installed from the installer.
Bug report feature constructor workflow.zip

Thanks