Standardized and Yet Flexible
Keep in mind that Yiddish is a living language, which means that it has influenced and continues to influence the language of the place where it is spoken. In short, the Yiddish language often borrows other words from other languages in the same way that other languages borrow from it. Despite such ongoing lending of words, literary Yiddish still possess a fairly standardized usage amongst speakers with a few exceptions to account for the place and time in which certain words are used.
Yiddish also exists in various dialects within the language that, more often than not, vary in both grammar and vocabulary. Again, this can be attributed to the many languages that Yiddish speakers come into contact with so much so that the differences in definition, context and even usage can be extreme. Yes, even the differences between American English and British English will pale in comparison.
And then there is also the fact that, if a foreign word does not have an equivalent meaning in the Yiddish language, it will be transliterated into Yiddish letters to come up with new words. Indeed, the Yiddish language being a living language, any Yiddish dictionary should try to keep up with the changes as these happen - if the publishers of the dictionary can do so, that is.
With all these information on hand, you will realize the importance of having an updated Yiddish dictionary on hand. Or at least, as updated as can be given the oft-fast changes happening in and to the language. Although the situation may seem unmanageable at first glance, it is actually manageable if and when you know where to start.