The following bug has been logged on the website:
Bug reference: 14547
Logged by: Kevin Welker
Email address: 385cbfd6(at)opayq(dot)com
PostgreSQL version: 9.6.1
Operating system: Windows 7 Enterprise
Description:
When you start expanding nodes on the object browser on the left hand side
in PgAdmin UI, the objects expand beyond the displayed size of the pane, but
no horizontal scroll bar is made available. The only workaround option is
to temporarily widen that pane, which takes away a lot of usable space in
the right hand pane.