In addition to Moecki's comment, I played around with the query syntax:
For Power-Up:
https://sds0.steemworld.org/transfers_api/getTransfers/{"type":"transfer_to_vesting","to":"lifetrail","fromTime":"1723593324","orderDir":"ASC"}/800
- direct call via URL
For Power-Down:
https://sds0.steemworld.org/transfers_api/getTransfers/{"type":"withdraw_vesting","from":"upvu","fromTime":"1723593324","orderDir":"ASC"}/800
- direct call via URL
To convert VESTS to STEEM, you can use steem_per_share
from this call: https://sds0.steemworld.org/steem_requests_api/getSteemProps
Maybe that's useful for you.