It’s only for a few weeks.
Apparently they both feed heavily on the same nutrients and would stunt each other’s growth if interplanted.
I wasn’t planning on planting them together. I was planning on planting one after the other (cabbage and kohlrabi in the spring and tomatoes, peppers and eggplant in the summer), but the first wasn’t finished when it was time to plant the second. So I researched the advisability of planting the second amongst the first. The answer was a resounding no.
But waiting would put me weeks behind schedule, so I did it anyway.
After harvesting two cabbages that were (almost!) ready, there was room on the end of the bed for two tomato plants. The eggplants went in where the kohlrabi came out. Then I just tucked the peppers in wherever there was a break in cabbage leaf-cover. That left me with 3 tomato plants and a pepper or two. The peppers I tossed (in the compost pile). The tomatoes I planted in grow bags.
I know I have to amend the soil in Bed #1 pretty heavily. If I encircle the root ball of each individual plant with compost (like a fertility forcefield) maybe all the dire predictions on the internet won’t come true.