Is your feature request related to a problem? Please describe.

When viewing MongoDB documents with Legacy UUID fields (Binary subtype 3), DbGate displays them as raw hex bytes. While v6.7.0 greatly improved binary field handling (#1240), there's no distinction between a generic binary blob and a Legacy UUID — both render the same way. This makes it difficult to read, compare, and work with UUID values that were written by Java, C#, or Python MongoDB drivers using the legacy format.

This affects any database created roughly between 2015–2020 with drivers that defaulted to Binary subtype 3 (Java, C#, Python). The BSON specification explicitly states that tools "should properly handle subtype 3". MongoDB's own Compass still has open feedback requests about this, and there are 16,000+ Stack Overflow views on related questions — it's a real gap across the GUI ecosystem.

Describe the solution you'd like

When a Binary field has subType: "03" (or "04"), display it as a formatted UUID string (e.g., 550e8400-e29b-41d4-a716-446655440000) instead of raw hex in the data grid.

The data already flows correctly — EJSON.serialize() preserves { $binary: { base64: "...", subType: "03" } } through the pipeline. The change would be in the display layer:

1. Detect $binary.subType === "03" or "04" in stringifyCellValue()
2. Format the 16 bytes as a standard UUID string with dashes
3. Preserve the subType on round-trip (edit → save)

Bonus (optional): Legacy UUID byte ordering varies by driver origin. An advanced version could offer a preference for the encoding (C#/Java/Python), but even without that, displaying the raw bytes as a UUID string is a major improvement over hex.

Describe alternatives you've considered

• Manually converting hex to UUID format outside DbGate — works but breaks the workflow
• Using Studio 3T for UUID-heavy work — proprietary, not ideal for daily use
• Migrating all data to subtype 4 — not always feasible with legacy systems

References

• BSON spec on subtypes: https://bsonspec.org/spec.html
• MongoDB driver UUID specification: https://github.com/mongodb/specifications/blob/master/source/bson-binary-uuid/uuid.md
• Related DbGate issues: How to display binary ID as hex instead of base64? #1240 (binary hex display), FEAT: MongoDB BSON Numeric Types Not Preserved (Causes Schema Validation Failures) #1154 (BSON type preservation), FEAT: MongoDB JSON display improvements #1264 (MongoDB JSON display)

I'm happy to contribute a PR for this if there's interest — the scope is narrow and the backend already handles the data correctly.