Re merge soundtrack into video

I am a relatively new user and have seen a couple of answers to similar questions, but these have been simple “drag and drop” text instructions, which I have been unable to replicate, so I need at least a screenshot to try and identify what I am doing wrong.
I am using Shotcut to slice up ripped VHS video tapes into smaller tagged and dated MP4s, which is going well. I am really impressed with Shotcut and am rapidly becoming a big fan.
One thing that I have noticed is that as I follow through my process, it seems to be quite easy to get my video and audio tracks out of synch. I am not sure how I am doing it, but that is not the problem, for whatever reason they are out of synch.

I have followed your How To guides to split these into separate tracks and spent some time to realign them, so that everything is re-synchronized and my question is how do I do it?

I hope my screenshot shows the problem, as whichever way I try to drag and drop the audio track back into the video it seems to insert the audio by splitting the video and inserting it…
Thanks in advance

Basically, the answer is you don’t try to merge edited audio back into the video; Shotcut and most video editors don’t work that way. There is no way to directly collapse a set of blocks into one block. Why did you detach the audio? That often creates more work than needed. Are you trying to silence the beginning? If so, you should instead use audio filters on the video clip with filter trimming or keyframes to do that. If you want to discard the detached audio clip and restore the audio in the video clip,: remove the audio clip and in the video clip’s Properties, choose Audio > Track.

If you want to keep the edited audio, you can use the Group feature in the latest 2 versions so they always move together. If you do not like the way Group works, you could export what you have and use the export file in a new project. Similar to that is a method that does not export, but you can include a project file inside another project. You use either FIle > Open MLT XML as Clip or simply drag a .mlt file from your external file manager and drop it into the timeline. If you do that, please ensure all .mlt files used together are using the same Video Mode (in Settings and New Project).

Thanks Dan,
What you are saying does sort of make sense, so I’ll try & answer your questions…
I detached the audio because the audio and video became out of synch, there was something like a 10 second delay in the audio which I was trying to fix by detaching the audio.
Now that the audio is re aligned I still have to slice the project into many more pieces which I want to save as multiple MP4 files. Will the Group function cater for this?
What do you recommend?

It depends on what you intend to achieve with “slice.” If you intended to use that to create multiple MP4 files, you should not. Instead, use range-based Markers. If you are slicing to remove portions of footage, Group is definitely a good way to go. Split now splits across multiple selected clips, and a group provides convenient re-multiple-selection.