Is your feature request related to a problem? Please describe.
Currently, query tool (in Connect tab) is great, but URI completion can be enhanced, be more accurate and complete.

Describe the solution you'd like

• suggest existing index names in current connection (in addition to API actions like _search)
• do not suggest "root" API actions that do not exist: _doc, _local, _only_node:, _prefer_node:, _primary, _primary_first, _shards:
• do not suggest "root" API actions that do not exist: _doc, _local, _only_node:, _prefer_node:, _primary, _primary_first, _shards:, count (without leading _), dfs_query_and_fetch, dfs_query_then_fetch, index, indices, preference, query_and_fetch, query_then_fetch, scan, search_type, stats, type, types
• when some index has been written with a trailing /, (say GET my_index/), suggest only API actions compatible with that case. So _search, _mapping, _settings are great. But these ones should be removed: _aliases, _cat, _cluster, _local, _nodes
• ideally, suggest only API actions compatible with chosen HTTP method. For instance, don't suggest "_bulk" when GET HTTP method has been written.

Additional context

• You can take some inspiration from this visual studio code extension (that uses also Monaco editor):
  https://github.com/hsen-dev/vscode-elastic
• There is also the official elasticsearch-specification (from Elastic) that can help:
  https://github.com/elastic/elasticsearch-specification/