Is there a way to import existing installations with custom paths into the program?

Here's how it's suggested to import already existing installations into the program:

You can also run the installers directly. As long as you have your portable apps installed to the standard location, they will automatically find your PortableApps.com drive, install and tell the menu to refresh.
- Adding PortableApps.com Format Apps to the PortableApps.com Menu

I highly suggest to replace the bold part with X:\PortableApps, just like you detail it in Adding Other Apps to the PortableApps.com Menu.

But my main question is what if I already installed various PortableApps programs into various locations?

I guess I'd like X:\PortableApps\PortableApps.com\Data\NewApp.ini to support custom paths, for example:
Replace:

[NewApp]
AppID=On-ScreenKeyboardPortable

With:

[NewApp]
AppID=c:\keyboard_apps\On-ScreenKeyboardPortable

Although preferably use relative folders:

[NewApp]
AppID=..\keyboard_apps\On-ScreenKeyboardPortable

Or Environment variables:

[NewApp]
AppID=%USERPROFILE%\keyboard_apps\On-ScreenKeyboardPortable