There is no auto reversal of accruals.  What I do is set up the entry, store it as a recurring entry, then post.

Recall the recurring entry, put a negative in front of each number, change the date and comment as necessary and post.

If the accrual is monthly and roughly the same, I normally set up a recurring entry for both on a monthly basis and post both as applicable.

That's depressing. I have been doing that as well, very time consuming.

I wonder why the hold up on this fundamental feature.

I can't really speak for the programmers as I don't work for the company.

I know years ago there was some talk about not being able to confirm exactly when an accrual should be reversed and they didn't want to lock anyone into being forced into a reversal if that was not the intent and may have to be edited, so completely automatic was not preferred.  There were other options suggested but not yet implemented.

Around 2003 I asked one of the programmers why there was not a customer PO field (as you say, a fundamental feature).  The response was that he had not been told to create it yet but he didn't know if other programmers had been told to do it.

Have you tried voting for it in the Ideas section of this website?  It's likely there.

If you're doing your accruals and reversals through the general journal, you could also try creating and editing your entries in Notepad and using the File-import feature.  Not nearly as seamless as if Sage had something internally, but potentially less manual fiddling around each month.  We have a Notepad template file for one of our clients and have had really good luck with copying and pasting entries into the 'live' Notepad import file, editing dates and numbers, and then pulling a whole pile of general journal entries into Sage at once.  

The three constraints are:

1. Must be in single user mode.

2. Must be using general journal.

3. Have to be careful with your number formats:  $1000.00 is good, $1,000.00 is bad, because every comma means "next field".