Navigating

The UV Editor has a 2D cursor. Its position can be changed by LMB clicking in the UV editor while the cursor tool is active. You can also manually adjust its position in the Sidebar region. The range by default is ranges from 0.0 to 1.0 starting from the lower left corner. By enabling Pixel Coordinates, the coordinates match the pixels in your image with XY(0, 0) located in the lower left corner.

2D Viewport

Panning can be done by clicking the MMB and dragging.

Zooming can be done by scrolling Wheel up or down. Also, as in the 3D Viewport, you can use NumpadPlus or NumpadMinus to zoom.

View Menu

Also see Navigating in the Image editor.

Frame Selected NumpadPeriod

Change view so that all selected UV vertices are visible.