There is no need for a special API route, "OR" logic is easy to implement. Merely search for each term separately and then merge the results.
For example, if I wanted tags that had either javascript or for-off, I'd first search for javascript(44 tags), then for for-off(2 tags), and then merge the results to get the 45 unique tag names.
Here's a complete‡ javascript, that you can run right now from your browser's console, that illustrates the process:
let baseSrch = "https://api.stackexchange.com/2.2/tags?pagesize=100&order=asc&sort=name&site=stackoverflow&filter=!-.G.68grSaJo";
var tagNames = new Set();
function getTagsByName (innameParam) {
return new Promise (otrResolve => {
fetch (baseSrch + "&inname=" + innameParam).then (response => response.json() ).then (rJsn => {
let zTags = rJsn.items;
let lclTagNames = [];
console.log (`Found: ${zTags.length} tags:`);
for (let tag of zTags) {
tagNames.add (tag.name);
lclTagNames.push (tag.name);
}
console.log (lclTagNames);
otrResolve ();
} );
} );
}
//-- Chain the API calls, for a consistent report...
getTagsByName ("for-off").then ( () => getTagsByName ("javascript") ).then ( function () {
console.log (`Final Result, ${ (Array.from (tagNames) ).length} tags:`);
console.log (tagNames);
} );
This gives results like:
Found: 2 tags:
Array [ "apps-for-office", "javascript-api-for-office" ]
Found: 44 tags:
Array [ "adobe-javascript", "amazon-javascript-sdk", "asynchronous-javascript", "embedded-javascript", ...
Final Result, 45 tags:
Set [ "apps-for-office", "javascript-api-for-office", "adobe-javascript", "amazon-javascript-sdk", ...
‡ Warning: Demo code only; not for production. Needs checks for XMLXHR errors, API Errors, and API warnings.