Answer
Yes — use the Export Language Files page: select 'export translations file,' the correct layer, type, module(s), and languages, which produces a zip of the translation data. Re-import it afterward via the Import Language Files page, ticking 'import translation files,' 'run as background job,' and 'refresh dictionary.' There isn't a way to export only specific translations — it's an all-or-nothing export for the selected scope — but running this export/re-import cycle after every service update is the practical way to preserve custom translations on core (not Config-layer) fields, since only core translations get reset by an update.