They share "junk", but nothing else (I have the two settlement perks). My small gripe is that I can't use it as a storage accessible from any settlement. That I can move past.

What kills me is that everything your merchants, scavengers, water purifiers, and other workers accumulate gets stored in that settlement's workbench. This causes you to stop at each one and with 10+ (I'm not that far into the story) that's a lot of time that could be easily bypassed, if workbenches shared everything.

So please Bethesda, or more realistically a modder, fix this.

This can be done - read this. http://attackofthefanboy.com/guides/fallout-4-workshop-guide-how-to-establish-supply-lines-between-settlements/

Unfortunately supply lines only share junk. I have mine all mapped out and it sort of shares things. For example if I put want to craft cutting oil, and have 50 purified waters in settlement A and 50 in settlement B, I can use the 100 to craft but I cannot withdraw them unless I'm at that specific settlement. Ifor I want to collect caps from merchants, the caps (or other items) are only in that settlement's workbench.

I know exactly what you mean by everything, EVERYTHING!
If I make a wall at sanctuary n decide I want that wall at Tenpines, Zimojima or The drive in I should be able too, but I can't!

Hopefully they patch that in!

Are you saying that if you put up a series of turrets in settlement A, for example, that it should replicate in Settlements B & C too?