I have the same problem with Mail-- I've searched, hoping that there's just something I'm missing, but apparently, according to this post, Apple has seriously degraded Mail. I've just emailed them as well, but all I can find is that these features have actually been removed in Catalina?! Seems like *bugs* to me -- Features that I used all the time (multiple times daily) are missing and infuriating! Why can't I:
* Sort by columns by clicking on column headings? Really, I have to select from a menu instead of clicking the heading? I've had to do this about 20 times already just this morning; slows me down. Just what I need, to be less efficient.
* Change column width: I hate the default. I want to change it back to my preference. I *hate* the default; it's distracting.
* Re-order columns: Seriously?! You know better than I do what I want/need to see to get my work done?
* View column showing that there is a file attachment: Seriously, Apple, what are you thinking? How am I supposed to find the ones that contain the documents I need without opening each email?
I get up to a couple hundred emails a day and I resent being slowed down by the removal of features that have helped me to deal with them! Please please put them back ASAP. Stop trying to make the Mac look like an iphone or an ipad. I pay a whole lot more for a Mac for a reason!