We have a handful of disabled Custom fields. The cleaning fairy (aka @NNichols ) tried to delete some in the past but it caused problems because there were still triggers attached to them. However, these fields should be removed from the triggers now so we could delete them (doesn't have to be maintenance week but we could do it now if we are able to confirm quickly enough)
select g.title, f.id, f.name, f.label FROM civicrm_custom_field f INNER JOIN civicrm_custom_group g ON g.id = custom_group_id WHERE
f.is_active = 0 ;
+--------------------------+-----+---------------------+-----------------------+
| title | id | name | label |
+--------------------------+-----+---------------------+-----------------------+
| Communication | 222 | Endowment_Opt_Out | Endowment: Opt Out |
| Communication | 223 | PG_Opt_Out | PG: Opt Out |
| Gift Data | 22 | Letter_Code | Thank You Letter Code |
| Gift Data | 53 | Thank__You_Stage | Thank -You Stage |
| PG - Commitment Activity | 290 | Country_of_Origin | Country of Origin OLD |
| Prospect | 11 | Type | Type |
| Prospect | 14 | Inclination | Inclination |
| Prospect | 136 | ask_amount | Ask Amount |
| Prospect | 137 | expected_amount | Expected Amount |
| Prospect | 138 | likelihood | Likelihood (%) |
| Prospect | 139 | expected_close_date | Expected Close Date |
| Prospect | 140 | close_date | Close Date |
| Thank you | 48 | Thank_You_Status | Thank-You Status |