Hi - that’s not currently possible, but definitely something that is actively desired by many developers - ultimately depending on some upstream work in the Wayland protocols, I believe. Some more links to read about this if you’re interested are:
KDE Community Wiki page for known issues: Plasma/Wayland Known Significant Issues - KDE Community Wiki
Explanation of that current state: Saving window placements on wayland
Bug report that has been tracking this: 15329 – Save and remember positions of all windows