Hardcoding height like this is extremely hacky and an anti-pattern.

Instead, can you please keep:

1. Make sure that stuff inside tagFarcasterChannelByName is always rendered
2. However, when selectedOption !== 'other', you can render it invisibly. I believe this can be done with visibility: hidden. That way, the appropriate amount of height for that stuff will be taken up, without you having to guess numbers that may or may not work across all browsers
3. Please review the rest of your stack for ANY and ALL hard-coded height, and replace it with this approach

Let's reorder this to reduce the number of branches the reader has to keep in their "mental RAM"

if (!selectedOption) {
  return;
}

if (selectedOption !== 'other') {
  createTag(selectedOption);
  return;
}

const channelInfo =
  await neynarClientContext.client.fetchFarcasterChannelByName(
    channelNameText,
  );
if (!channelInfo) {
  setError('channel_not_found');
  return;
}
createTag(channelInfo.id);