Opening the UI and loading a file is possible: https://creator.pdf24.org/manual/11/#911-open-the-ui

Use the -outputFile FILE, -noProgress and -profile switches, depending on the command switch, which is curently not in the command above. Please read this: https://creator.pdf24.org/manual/11/#111-command-line

Next version of PDF24 Creator is on the way and will be released in a few days. This version brings improvements regarding PDF/A generation. The online tools usually get the latest developments quite quickly,...

I think you can use the Split PDF tool and there use the halven pages mode. This splits the pages in the middle.

You can configure the PDF printer so that it saved automatically. Then this UI would not pop up. I think it's a good advice to install a new PDF printer for that because here and there the default PDF...

Seems that you have associated the file type with one of the PDF24 apps. You can change that via the open with context menu entry or via the default apps sections in Windows settings.

Currently not. What key combination would you recommend?