I have a junior to point to new Dolphin contributor.
Feel free to claim it here:
Details
This is an extension to On middle-click, open file with the second application for the file mime (!596) · Merge requests · System / Dolphin · GitLab
The modifier would need to be transmitted to DolphinViewContainer::slotfileMiddleClickActivated from DolphinView and `KItemListController::itemMiddleClicked`(src/kitemviews/kitemlistcontroller.cpp · master · System / Dolphin · GitLab) and then can pick a different application depending on the modifier.
And makes this discoverable as DolphinContextMenu: Add hint that secondary app will be opened by middle click (!737) · Merge requests · System / Dolphin · GitLab did as well.