Is there a Cross Reference code that does not replace the existing text?

[jtwork]

I want to *type* the arbitrary block of text, have that block be clickable and jump to some arbitrary place without replacing the originally typed text with anything at all.

<$paratext> overwrites the text I've typed with the text of the xref's destination.  I don't want to overwrite anything - I just want to go to the destination.

(I have a Part List - and I want to highlight the Part Number and have it linked to the Parts Page. However the Cross-Reference includes the Part List and Description, which is too long and does not fit in the table. I do not want to include the Page Number, since I want to keep the table simple and uncluttered.)

[LinSims]

Your simplest choice would be to format the Part Number with its own paragraph tag so that you can link to it directly with the xref. If you make it a run-in header, I think you'll be able to keep it on the same line with the remaining information. As far as the xref is concerned, only the number will be picked up during generation. (I haven't really worked with Run-in Headers, though, so I could be wrong.)

If that's not a possibility, you'll be stuck with inserting a Specify Named Destination marker at the Part Number, then selecting the words "Part Number" at the origination point and adding a hypertext Jump to Named Destination marker in the Part List and, possibly, giving it a character format so it looks like a link. 

[frameexpert]

You can use gotolink/newlink Hypertext markers. You put a newlink marker at each part number, then where you want the text to be a link, insert a gotolink marker and format it with a character format.

[Matt S - Tech Comm Tools]

To clarify Rick's reply, apply the character tag to the marker and text to be used for the link. 

It's not necessary to format the text, per se; the character tag could be fully set to As Is, but if no character tag is applied, then the entire paragraph will be the active link.

Perhaps not a problem, unless you have more than one hyperlink in a given paragraph. At that point it gets a bit confusing for the audience.

[frameexpert]

I will add that this can be a tedious process if you have a lot of links to part numbers and this could be automated with ExtendScript. Disclaimer: I make a living writing scripts like this.

[K.Daube]

I have done this with the method Lin proposes (paragraph tag part-no, x-ref to these paragraphs). I have even overplayed small frames on graphics with the parts and inserted the x-refs there.