Sure it is.
I triple boot to DOS, Win98SE, Win2000 or WinXP.
I create a 2 GB FAT16 DOS primary partition, a boot manager primary partition (in my case it's a Win2000 NTFS partition which I also use as boot manager), a 2 GB logical partition for data exchange. Finally I create the FAT32 Win98SE partition.
It is important that the Win98SE partition starts not past CHS cylinder 1022 (~8 GB), so it will have a huge size then (~90 GB).
You need a kind of disk editor to hide other primary partitions while you install the 2nd and 3rd operating system. This tool also helps you to safe the boot sector of both DOS and Win98SE partition as file, and to copy them on the Win2000/XP partition if you use that as boot manager.

The problem is that Win98SE is already installed, and I have to move the Win98SE partition up a little to make room for DOS/Win3.1. Where can I find the partition-editing and boot-up tools? BTW, I have some experience with FDISK and FORMAT but want to keep the current Win98SE partition.

A tool like Partition Magic can do this

Thank you. I'll Google it now. 😀

I found Partition Wizard instead, and it requires an extra download. 🙁

I looked back and found it. Thanks! 😀