Here's a page listing all Wikidata tools that I find useful: you can also find gadgets and user scripts order alfabetically.
Tools
Main tools for generating and processing data in Wikidata.
1Cradle
Description: A tool for Wikidata item creation.
Use case: When you need to create a new item in Wikidata, Cradle provides a user-friendly interface form to input the necessary information and generate the item efficiently.
2Open Refine
Description: Tool for Wikidata massive edits.
Use case: Use Open Refine to reconcile data, clean datasets, and upload large batches of structured edits to Wikidata.
3Quickstatements
Description: Tool for Wikidata massive edits.
Use case: Ideal for bulk editing statements and IDs across many items using preformatted commands.
4Recoin (Relative Completeness Indicator)
Description: Tool that adds a status indicator to Wikidata pages and shows two expandable lists of important absent properties and IDs.
Use case: Helps identify missing key statements and identifiers, making it easier to improve item completeness.
5Wikibase Query Service GUI
Description: Interface for building and running SPARQL queries against Wikidata with a graphical query builder.
Use case: Useful when you want to explore Wikidata data visually or construct queries without writing raw SPARQL from scratch.
Gadgets
Small interface enhancements and helpers for Wikidata editing.
1Duplicate References
Description: Gadget that adds a link to copy references and add them to other statements on the same item.
Use case: Save time when multiple statements share the same source, by duplicating references across statements with one click.
User script
Scripts that extend Wikidata UI functionality per user account.
1Quickpresets
Description: User script that allows you to add common statements with only one click.
Use case: Streamline adding frequently used statements by selecting presets instead of manually filling each property.