I find this part of Amibroker a little irritating. Navigating the chart shouldn't be cumbersome.
If Captain Black's idea of using an independent window wasn't what you were looking for, try this - If you move the mouse cursor over to the scale on the right of the chart the cursor will turn into a double headed arrow. Hold down the shift key and drag the mouse. it will change the scale of the volume pane. Effectively zooming in.
Unfortunately when you change the scale it uses the middle of the chart as the reference point. So you then have to release the shift key and drag the volume scale up to get the zero level back on the screen. You can also double click on the scale to reset it to normal.
The reason I don't like using an independent window for the volume chart is that zooming in on either window means the volume bars no longer line up with the price bars.
If anyone knows how to change the volume scale while keeping the zero point fixed at the bottom of the screen please let me know.
Try this snippet of code:
scalingVolumeHeight = Param( "1/n Volume Height", 5, -1, 10, .05 );
Plot( Volume, "", color, styleHistogram|styleownscale, scalingVolumeHeight);