Issues with advanced key mapping

### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

-When creating a macro with advanced mapping, trying to insert a 2nd slot, makes it add 2 more instead. (for a total of 3 empty ones)

-When it adds the extra one for the 2nd field, it also resets the mapped key for the controller button
(Close advanced and reopen it and it will say that there is nothing assigned)

-Adding a key in front (to the left) of an other one, removes the one to the right

### Expected Behavior

-It should add only 1 more slot instead of 2. Clicking the insert button for a 3rd time only adds 1 more slot

-The key shouldn't be reset, in the old AntiMicro it didn't reset either when you put a key in the advanced mapping

### Steps To Reproduce

- [x] 3 Slot issue:
-Open mapping for any controller button
-Choose any key
-Click Advanced
-Click the button you just assigned but in advanced mapping
-Click the Insert button 2 times

- [ ] Key reset:
-Do all the steps above
-Close advanced mapping and try to reopen it, the assigned key is gone

- [ ] 2nd key removes 1st one:
-Open mapping for any controller button
-Choose any key (e.g. 'G')
-Click advanced
-Click the button you just assigned, in advanced mapping window
-Click insert 1 time to add a slot
-Click the new slot and add any key (e.g. 'X')
-Close advanced mapping
> Instead of being 'XG', it is just 'X'

### Environment

```markdown
- OS: Windows 10
- AntiMicroX version: 3.2
```

### Anything else?

Also took a clip which tried to showcase all 3 issues

[https://puu.sh/Imn12/f5503cfe82.mp4](https://puu.sh/Imn12/f5503cfe82.mp4)

Timestamps
3 slots + key being reset
0:05 - 0:30

Adding 2nd key removes previous one
0:30 - 0:55