Improve UX to reduce/increase level of belt or pipe

Currently, when selecting a belt or pipe we only have an upgrade button. Clicking this button while ignoring the tooltip upgrades the belt.
If the belt is max level, clicking this button downgrades 1 level. Clicking it again, will upgrade 1 level.
Proposal:
It would be nice to either have 2 buttons to upgrade and downgrade separately. Gray out the one that's not possible when at min or max level.
This would be best for discoverability.
Alternatively / additionally, add shortcuts to upgrade / downgrade from the building window directly without having to use the upgrade tool (which can't downgrade).