How do I remove the battery cover?

Can you remove the cap that you are pointing too in the photo? not sure what you mean by A +. Is it a hex or star pattern?

It is (was) a + like a Philips head bolt. It's plastic. It is turn-able in its hole; it doesn't seem to want to pop out. It looks like a big hole in the picture because I've stuck my screwdriver in through it, looking for a bolt or screw underneath. The flaps created by the plus cut are now permanently deformed, although there is still a bit of the cuts at the outer edge that can be used as leverage points to turn this plastic cap thingy. But nothing seems to unscrew as I turn it. Before I go at it with a vengeance, tear it apart, and destroy it in order to get to the battery, I thought I would check and see what experience and advice others might have. I'm sure there's some sort of trick to removing the battery cover. There doesn't seem to be any video or other DIY description on removing this cover on the 2016. Other years, but not mine, that I've found. It's rather irritating that the owner's manual shows us where the battery is, says "remove the battery cover" with a simple up arrow in the drawing, but no mention of the clips on the front part, or whatever it is that is catching in the back.

I just pulled hard for my 2018 hybrid highlander, and the inserts holding the cover pulled out. It is not easy. The 2018 battery holding area and covers are poorly designed. the new highlanders have a better access method, and the battery is located on the the passenger side instead of the driver's side.

On my 2016 HiHy the battery cover has pry snaps. If you use one of the curved auto body plastic pry bars at the attach points , just pry up the bottom first and the rest should follow. A flat screwdriver also works if you are careful. A separate panel pulls off just above the battery cover for access to the top bracket screw.