@8887bdb192, personnally, I finally achieved to install some plugins behind my proxy.
Parametrizing proxy in menu “Window, \ Katalon preferency \proxy in manual mode” let plugins to install.
I had some PKIX problem and solve it by adding my company certificate to java (see this post for more informations about solving this pkix issue here: Unable to upload Report from Katalon Studio to Katalon Analytics) .
Only problem for me is that I cannot let proxy configured as I need to test on internal company website and proxy is set for tests as for plugins and analytics.
If an exclusion list is developped, it will allow me to use again some Katalon plugins (see this tread Basic Report plugin - Proxy Setup Issue and linked issue https://github.com/katalon-studio/katalon-studio/issues/179)