' if there are lots of folders within the current project folder'
What is the range for 'lots'? I feel this representation is 'several'.
Here is a sample from one project folder. That folder is what is loaded IDE >> Settings >> Project :: Select Directory for Sandbox
These are the folders there, created when the native IDE selects the project after clicking the button above.
Most are empty of files, 1-4 in modules, 1-~10 in projects, 1 in snippets.
C:\EspruinoMQTT \binary \firmware \modules \projects \snippets \testing \testinglog
At most a list of ~25 individual items beneath each project folder.
That should be the case - however if there are lots of folders within the current project folder I guess that could slow things down?