MK4S+MMU3 - Can't modify other extruder settings without saving modified ones

[Mike-FUT]

Description of the bug

What is the problem? In PrusaSlicer (I tested 2.8.0 and 2.8.1 RC1) for MK4S and MMU3 when you change filament settings for one of the five filemants you can't change any other filament from other tool numbers without saving the changes first. Also as soon as I change another filament the settings of the filament I did before will get lost.

What did you expect?

1. Same behaviour as everywhere else in PrusaSlicer: Any setting (Printer, Filament, Print Settings) can be changed and used for slicing without having to save them first.
2. Settings don't get lost.

Why is that important? I'm using a mix of PETG/PLA filaments on my MK4S+MMU3 to use the PLA as support interface for PETG and vice versa. When doing so I'm adjusting the bed temperature of the support interface material to match the bed temperature of the main material. But I certainly do NOT want to store a new profile for that because otherwise I'll have to compare with each configuration update. Now let's say slot 5 is PLA (support interface) and slot 1 is PETG (main material) and I'm changing bed temperature of slot 5 PLA and then I want to change any parameter in slot 1 a popup will show if I want to transfer or discard the settings. No matter what I choose - settings on the PLA slot 5 will get lost.

Project file & How to reproduce

1. Select MK4S/MMU3 printer profile
2. On the right side of the screen (Section "Filament") assign PLA to slot 5 and PETG to slot 1 of the MMU
3. Click on the settings wheel for slot 5 PLA and modify it to match the bed temperatures of slot 1 PETG
4. Try to Modify the settings of slot 1 PETG

• The popup to transfer settings should NOT show up now. It logically doesn't make any sense and it doesn't work that way anywhere else in the slicer. It should always allow you to modify other settings without having to save first.
• Even worse - no matter what you choose from the popup, settings from slot 5 PLA will be gone afterwards as long as you don't cancel but then you can't modify slot 1 PETG

Technically: I guess modifying another filament on another slot is triggering the same behaviour in the software as selecting a new filemant after changing the current filament (like in a single-extruder non-mmu setup). But it shouldn't since no new filament is selected.

Checklist of files included above

• [ ] Project file
• [ ] Screenshot

Version of PrusaSlicer

2.8.0, 2.8.1 RC1

Operating system

Windows 10

Printer model

MK4S + MMU3

[Samuel1698]

Agree that this needs to be fixed/implemented

[Ro3Deee]

Same on Prusa XL (5 tools)