Welcome to MT Drew! Hope you enjoy your stay and join in
Yep, sparring is with a partner, and a lot of things there can't be developed without one.
BUT... hehe, you can still do a lot of drills that will still enhance your sparring. Again, not a replacement for sparring with a partner, but when I was training on my own all of last year, the first tournament I entered I had absolutely no training partner to practice with. I ended up winning my first bout and coming very very close to winning the finals, so ended up with silver.
Now I know that a lot of my prior training helped out a lot here which must have kicked in, but I researched like crazy, got creative, and developed a solid routine 10 weeks or so before the tourney.
I did things like:
-plyometrics (not only normal explosive bounces, but bouncing and as SOON as I land, exploding forward with a technique)
-aLOT of footwork drills (even drilling simple steps a great deal, stepping front foot forward, shuffling back foot up, stepping through with back leg), combining these with different techniques and parries, stepping off to the side and at angles with counterattacks
-reaction drills like setting my phone to do random beeps with an app and reacting with a block and counterattack or just attack as fast as I possibly could
-swinging a tennis ball on a string and stepping off to the side as it almost hits me constantly whilst dodging it, parrying it or attacking (also doing this with eyes closed, and opening my eyes at the last second before it would hit me and reacting)
-setting an object on top of a chair back, and practising distancing, trying to come close as possible to hitting it etc
-bagwork
-and of course, a lot of shadowsparring rounds, with a lot of visualisation too. Visualising the person in front of me, what they're attacking with, how I would react etc
But yeah these are definitely more supplementary, but can definitely help sparring. Sometimes in sparring it's too heated and intense, and a lot of people just freeze up and aren't allowed the opportunity to really trial things out and practice as it's too high pressure. So working on relaxing while simulating sparring on your own can help a bit. But no substitute for partnerwork