" I could work on something at the 8 minute mark and leave everything alone there while I jumped to minute 3 or something to work on that section."
When I edit music videos I deal with the same kind of thing. I tend to use Gap Clips (option w to insert one into the Timeline). Then highlight it (by clicking on it or tapping "c" when the playhead is over it) and hitting Control D and typing the length you need it to be, then hit enter or return. Or just drag it to the length it needs to be.
There are also Placeholder clips under Elements in Generators but I rarely use them unless I'm handing off an edit to someone else. Option Command 1 > Generators > Elements >Placeholder
The timeline will still lengthen or shorten with Gap Clips or Placeholders if you add/remove things. For that you can use the standard overwrite or replace edits and even slips and slide edits. One thing to maybe get famlier with is the Position tool (tap "p" for it):
Arrange clips in the timeline in Final Cut Pro for Mac - Apple Support
"Overwrite clips using the Position tool"
You can use the Grave accent key (it's right above the Tab key on keyboards) in conjunction with the Position tool to move clips and break links.
Connect clips in Final Cut Pro for Mac - Apple Support
"Edit clips in the primary storyline without affecting connected clips"
Also, I find Markers incredibly helpful when editing, especially things I use gap clips a lot in like music videos and documentaries. Option M will insert one and give you options on what kind etc...
"I went back to the timeline and NONE of the clips were labeled? ALL of the corrasponding clips I've already been editing were not effected at all?"
This is a problem, yup. Totally agree. If there is a way I don't know it.
The reason is the "clips" in the timeline aren't the same "instance" as the clips in the Browser.
I totally understand why Apple does this, however, it would be nice to have a function that's something like "Assign Roles to Timeline Clips." which reminds me I need to send feedback to Apple about this again :)
I often get libraries and XMLs from editors that didn't assign roles to stuff before they begin editing so my workaround is this:
Open the Timeline Index (Shift Command 2) then click on Clips. Then type in the beginning of the clips I need to assign roles to, highlight them in the Timeline Index, then in the Timeline itself, right-click and assign them the role I need (or use the Role keyboard command). You may not see their color change right away, so sometimes I double check them by toggling their Role in the Timeline Index. Alternately, if you have the roles columns visible in the Timeline Index you can highlight and change clip's subroles there by right-clicking on the subrole in the column, but I think that's just for subroles.
But yeah, Apple could improve this, totally with you on that.