Mouse without borders not intuitively usable - every time I try to add another PC, all others vanish

### Microsoft PowerToys version

0.100.1

### Installation method

Chocolatey

### Area(s) with issue?

General, Mouse Without Borders

### Steps to reproduce

Hi.
Why is it so complicated to add computers to one's list?
It sadly really is not intuitively usable - every time I try to add another PC, all others vanish.
Under "Enryptionkey" I expand the fields and add the new key from another PC and its name and click on "connect".
What the heck am I doing wrong?

### ✔️ Expected Behavior

To add an additional device.

### ❌ Actual Behavior

Now it's the only device avaiable in my list.

### Upload Bug Report ZIP-file

_No response_

### Additional Information

_No response_

### Other Software

_No response_

Start by reproducing the reported flow in Mouse Without Borders on PowerToys 0.100.1: add another PC using the encryption key and name, then select Connect. Done means the new PC is added while previously configured PCs remain available; no source files or tests are named in the report.

Written by the indexing model from the issue text.