This may simply be because I haven't been using projects in Slick for years, but I'll give the feedback anyway.
Setting up a python project, I noticed a bad default for my interpreter was set.. I'd uninstalled it to get a newer version. I couldn't for the life of me find where to correct the interpreter pathname for a while. I found it in my project, but it would be very nice if (for something so common as primary system tools), I could find that setting when I look at Tools->options and search on "python". There's a whole subtree for python stuff -- no binaries. It'd be nice if pyenv versions were detected as well and perhaps I could be offered a list to choose from.
PS. It's buried in project properties->Tools->Execute->Options, then at the bottom of the dialog. I kept missing it because all settings are near the top, while the interpreter is down by the OK button. Eyes are drawn away from it.
PPS. Before I found it in the GUI, I followed the bunny trail of seeing SLICKEDIT_PYTHON_EXE in project setup. In the help system, I found the actual variable, so I I fixed it with:
set-var def_python_exe_path