How to get all active snippets for a given language programmatically in extension?

Here is something you might be able to adapt to your needs. You can use the command vscode.executeCompletionItemProvider to return all "completions" relevent at a position.

Those completions can then be filtered to only include snippets.

Consider this code:

// Code-Lens-Action insert-snippet wsNameFolder _cc

where the snippet prefix is _cc and the snippet name is wsNameFolder.

const doc = vscode.window.activeTextEditor.document;
const thisUri = doc.uri;
const pos = vscode.window.activeTextEditor.selection.active;
        
/** @type { import("vscode").CompletionList } */  // if using javascript
const completionList = await vscode.commands.executeCommand('vscode.executeCompletionItemProvider', thisUri, pos);
        
let filteredList = [];
        
const word = doc.getText(doc.getWordRangeAtPosition(pos));
let good = undefined;
        
if (completionList && completionList.items) {
  filteredList = completionList?.items.filter(item => item.kind === vscode.CompletionItemKind.Snippet);
        
    // does the filteredList (of snippets) contain one with a label that matches the "word" 
    good = filteredList.find(snippet => {
        if (typeof snippet.label !== 'string')
            return snippet.label.label === word;
    });
}

Triggering the executeCompletionItemProvider with the cursor immediately after or within _cc will get those snippets that match that prefix.

But, triggering the executeCompletionItemProvider with the cursor immediately after or within wsNameFolder will still treat that name as the prefix to find matching snippets. Which likely won't work for you.

Also. triggering the executeCompletionItemProvider in an empty area - not immediately after or in a word will work. You will get all suggestions that can then be filtered. If the cursor is before the name that works too.

So I don't know where you plan on the cursor being on that line. If it will be after or in the snippet name you should be able to calculate the position immediately before the name and use that position in the executeCompletionItemProvider call.

The following code gets the Position just before the snippet name. Using that you get all suggestions. Filter that for snippets and then find the one where the snippet.label.description matches the snippet name. It is a little confusing but snippet.label.description is really the name and not the snippet description.

"wsNameFolder": {             // I assume you are using this
  "prefix": "_cc",
  "body": [
    "${WORKSPACE_NAME}"
  ],
  "description": "Workspace Name and Folder"   // not this
},

If you are really using the description above, you can find that too - that info is in the snippets returned.

const doc = vscode.window.activeTextEditor.document;
const thisUri = doc.uri;
const pos = vscode.window.activeTextEditor.selection.active;

const nameStart = doc.getWordRangeAtPosition(pos).start;

// const completionList = await vscode.commands.executeCommand('vscode.executeCompletionItemProvider', thisUri, pos);
const completionList = await vscode.commands.executeCommand('vscode.executeCompletionItemProvider', thisUri, nameStart);
let filteredList = [];
        
const word = doc.getText(doc.getWordRangeAtPosition(pos));
let good = undefined;

if (completionList && completionList.items) {
    filteredList = completionList?.items.filter(item => item.kind === vscode.CompletionItemKind.Snippet);

    // does the filteredList (of snippets) contain one with a label that matches the "word" 
    good = filteredList.find(snippet => {
        // return snippet.label.label === word;
        if (typeof snippet.label !== 'string')
            return snippet.label.description === word;
    });
    
console.log(good);
}

Assuming there are any empty lines, this seems to return all the suggestions that can then be filtered to Snippets:

const text = doc.getText();
const emptyLines = [...text.matchAll(/^$/gm)];

const firstEmptyLinePos = doc.positionAt(emptyLines[0].index);

/** @type { import("vscode").CompletionList } */ // if using javascript
const completionList = await vscode.commands.executeCommand('vscode.executeCompletionItemProvider', thisUri, firstEmptyLinePos);