When i run bitcoin-qt.exe with -zapwallettxes parameter, it rescan my wallet, but using only 1 of 20 core ~6.6% of maximum, and only 60-90 MB/sec reading on M2SSD drive. How can i add more cores for running QT ?

https://i.imgur.com/zNQMgJ3.png
^{bitcoin.conf = dbcache = 20000 par = 15 txindex = 1 addresstype = legacy proxy=127.0.0.1:9050 listen=1 bind=127.0.0.1 onlynet=onion datadir=E:\Roaming\Bitcoin blocksdir=E:\Roaming\Bitcoin}