I was trying to get the appropriate devanāgarī for trīl̃lokān (cf.
https://archive.org/details/sanskritgrammari00whit/page/69/mode/1up especially the middle versoin without virāma), but it seems like most of these sites cannot handle it. If someone is going through all of them and checking for accuracy, this might be one instance where some improvement is required (e.g. aksharamukha will give त्रील्ंलोकान् using either IAST or ISO 15919 for the input). The Sanskrit Library provides the last of the three versions Whitney gives, i.e., with candrabindu and virāma, but that might be a limitation of available glyphs. I would be interested to know which typefaces can offer the second of the three versions in Whitney.