As far as I know you can keep the default path also you can change the path too while installing Electrum. Not sure which plugin you are playing with.
So I downloaded the version again off
https://electrum.org/#download and reinstalled it and it created Electrum Testnet folder and I open it works fine but when I try to open my old wallet on this new installation I get this message:
"cannot load wallet the addresses in this wallet are not bitcoin addresses"
But I can still open that wallet using my desktop icon for that wallet.
I have 2 Electrums installed now. The new one I was able to put in that plugin.
So why cannot the new installation of Electrum open my old wallet?