Skill Tree's pump bar has a default value of:
"Anchor points": {
"anchor_min": "1 0",
"anchor_max": "1 0"
},
This anchors to the bottom right corner of the screen, near the health bar. You can adjust the distance and size of the bar with the offset values.
Changing the values in the config does not change for all players who have connected to your server already, as Skill Tree allows for individually set xp bar points.
You can force an update for yourself using the /resetxpbar command, or you can update it for all players using the /resetxpbars command.