I don't know if this is possible - but how can I make it so that the contents of a portal are visible _all the time_, even when the user is moving the portal view by dragging the scrollbox in the scrollbar?

The contents are visible when scrolling, but only if you use the up/down arrows in the portal's scrollbar. If you drag the box, the display locks until you stop moving. This makes finding items in a long list somewhat slow.

You can't change the scrolling behavior, but if the number of records in your portal is too high to easily scroll through, you should consider adding a filter to they portal so you can reduce the number of records found.

For instance, search the forums for "clairvoyance", and you will find a way to type the first few character of a field into a search (global) field, and you'll be able to reduce the list down to only the matching items.