I think this is specifically more an IME (input method software) issue than a typing one. Japanese has similar "official" numbers (壱, 弐, 参, maybe some of the few cases where modern Japanese is more simplified than Simplified Chinese).
These numbers couldn't be easier to type. I just type 1, 2, 3 (i.e. the digit keys on top of my keyboard), hit the convert key and select the right character (I also get offered 三, ③, 3⃣,³ and several other options to choose from). That's it.
I tried the same with Google's IME and I couldn't use digits as input, like the Japanese IMEs let you do. I could find the character for 叁 quickly enough, but 壹 was only on the second or third page. Still, I suck at Chinese and I found it.
Now, writing these characters is an entirely different story. I think any character that's rarely written and appears only in one common word runs the risky of being forgotten, even if that word is quite simple and used on a day-to-day basis. A word like 喷嚏 (sneeze) in Chinese or 薔薇 (rose) in Japanese fit the bill.
The Japanese fallback, in case you forgot the character is quite simple: you'd just use either Katakana or Hiragana with different connotations[1]. I'm not quite sure what the fallback would be in Chinese, but I guess that would often be picking another character with a close or same pronunciation, as Chinese speakers often do on purpose as a sort of pun.
I also expect there are still fewer cases of "character amnesia" in China than Japan, since the fallback mechanism is simpler and more standardized in Japan, and children are taught far less Kanji in school than their counterparts in Mainland China, Hong Kong or Taiwan.
[1] While Hiragana gives a familiar connotation, writing the word as バラ in Katakana is "more official", if anything, since names of flora and fauna are conventionally written using Katakana in official contexts, especially when you want to use the exact scientific name. This is the equivalent of using Latin names in Western countries, e.g. Rosa hirtula would be サンショウバラ.
I tried the same with Google's IME and I couldn't use digits as input, like the Japanese IMEs let you do. I could find the character for 叁 quickly enough, but 壹 was only on the second or third page. Still, I suck at Chinese and I found it.
Now, writing these characters is an entirely different story. I think any character that's rarely written and appears only in one common word runs the risky of being forgotten, even if that word is quite simple and used on a day-to-day basis. A word like 喷嚏 (sneeze) in Chinese or 薔薇 (rose) in Japanese fit the bill.
The Japanese fallback, in case you forgot the character is quite simple: you'd just use either Katakana or Hiragana with different connotations[1]. I'm not quite sure what the fallback would be in Chinese, but I guess that would often be picking another character with a close or same pronunciation, as Chinese speakers often do on purpose as a sort of pun.
I also expect there are still fewer cases of "character amnesia" in China than Japan, since the fallback mechanism is simpler and more standardized in Japan, and children are taught far less Kanji in school than their counterparts in Mainland China, Hong Kong or Taiwan.
[1] While Hiragana gives a familiar connotation, writing the word as バラ in Katakana is "more official", if anything, since names of flora and fauna are conventionally written using Katakana in official contexts, especially when you want to use the exact scientific name. This is the equivalent of using Latin names in Western countries, e.g. Rosa hirtula would be サンショウバラ.