The WebSearch add-on gramplet by @urchello already supports storing external IDs with Attributes. But you need to be able to search… both for particular ID values and for particular built-in and custom types.
| Attribute name | Website | Description | Example value |
|---|---|---|---|
| _FSFTID | FamilySearch.org | person profile | KNDX-MKG |
| FacebookID | Facebook.com | account | groups/370692133138445 |
| FindAGraveID | FindAGrave.com | memorial profile | 1075 |
| GeneeeID | Geneee.org | (Geneweb) person profile | george/washington |
| GeniID | Geni.com | person profile | George-Washington-1st-President-of-the-United-States/6000000008211776777 |
| GNDID | d-nb.info | Dun & Bradstreet business profile | 54-0564701 (Mount Vernon Ladies’ Association of the Union) |
| InstagramID | Instagram.com | account | @mount_vernon |
| LinkedInID | LinkedIn.com | person professional profile | mountvernon |
| RogloID | Roglo.eu | (Rauglaudre collaborative GeneWeb database) person profile | 1825727 |
| VIAFID | viaf.org | (Virtual International Authority File) OCLC identifier | 31432428 |
| WeRelateID | WeRelate.org | person profile | George_Washington_(6) |
| WikidataID | Wikidata.org | knowledgebase article name | Q23 |
| WikipediaID | wikipedia.org | knowledgebase article name | George_Washington |
| WikiTreeID | WikiTree.com | person profile | Washington-11 |
| XINGID | XING.com | job listing |
The TypeCleanup addon tool will let you search for the existence of Custom types… but not built-in types.