A second observation after reading this thread:

In this post zaq (no relation) discusses using the drilled in port to simply vacuum off the screen:
https://www.oregonperformancetransmissi ... creen=SRCH

In this post firstv70volvo noted that with the valvebody removed there is a passage leading directly to the topside of the filter screen:
search.php?keywords=previous+dealer&t=82841&sf=msgonly

Given the above, if one were planning a valvebody swap, wouldn't it be useful to drill a hole as noted here:

fill the filter with 3309 or possibly a nonflammable solvent, and use a vacuum with an inline drop out chamber to simply clean off the screen?

In this way the screen would still keep contaminants out of the passages of the valvebody and transmission, while avoiding pressure drop that would reduce line pressure or lead to pump cavitation/whine.

I read with interest about the clogged filter and wondered how many transmission problems are caused not only by a completely clogged filter but a partially clogged filter that reduces fluid flow. The previous dealer installed transmission in my car had a whine while cold and now I understand what was likely the cause. The transmission has since been replaced by the dealer due to the whine even though it was beyond the warranty period.
After 70K miles the latest dealer installed transmission started having delayed engagement problems so I replaced the valve body and all has been fine now for 10k miles since VB replacement.

From the valve body work that I've done there is access to the pump suction port (and top side of the filter) when a small cover is removed from the valve body on the lower left side. I'm thinking this access port could be used to back flush the filter while the drain plug is removed. Has anyone ever tried this? It might require a small plate to better seal the valve body opening and then compress air and fluid back flushing could be done. While back flushing what drains out of the transmission will be a good indication if this is effective or not.